Azeotropic dehydration of 1, 1&#39;-oxybis-(2-chloroethanol)



fiatented eh. 6, 1 95i AZEOTROPIO DEHYDRATION F 1,1'-OXY- BIS-(Z-CHLOROETHANOL) Stephen C. Stowe, Midland, Mich., assi or to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Application July 15, 1948,

Serial No. 38,947

8 Claims.

This invention concerns an improved method of dehydrating 1,1-oxybis-(Z-chloroethanol) to form chloroacetaldehyde. It relates more particularly to the production of anhydrous chloroacetaldehyde by dehydration of concentrated aqueous chloroacetaldehyde and 1,l'-oxybis-(2- chloroethanol) solutions.

It is known to prepare chloroacetaldehyde by introducing chlorine and vinyl chloride in the gaseous state into water at cool to moderate temperatures,e. g. at from 0 C. to 40 C. Recovery of the chloroacetaldehyde from the dilute aqueous acid solution has heretofore been accomplished by increasing the concentration of hydrogen chloride in the reaction mixture to approximately per cent and thereafter distilling the aqueous acid mixture to obtain chloroacetaldehyde in a concentration of from '70 to 80 per cent. By passing the distillate vapors over a layer of calcium chloride, heated to 100 C., anhydrous chloroacetaldehyde has been obtained. However, this known mode of dehydrating the chloroacetaldehyde is costly and inconvenient. When the concentrated aqueous solution of 70 to 80 per cent chloroacetaldehyde is redistilled and the vapors condensed directly, there is obtained a product, distilling at 85-85.5 C. at atmospheric pressure, which has heretofore been referred to as a hydrate of chloroacetaldehyde. The product crystallizes to a solid at room temperature, has a chemical composition corresponding to the formula CH2C1'CHOH-O-CHOH'CH2C1, and may be named 1,1 '-oxybis- (2-chloroethanol).

Attempts to convert this material to anhydrous chloroacetaldehyde by usual dehydration procedures such as treatment of the material in liquid form with solid drying agents, e. g. calcium chloride, sodium hydroxide, calcium sulfate, anhydrous sodium sulfate, activated alumina, etc., results in failure, or poor yields of chloroacetaldehyde product. Extraction of the material with organic solvents such as ethylene dichloride,

benzene, toluene, ethylbenzene, hexane, tetra is so small as to render the process impractical for industrial use. Apparently, such solution contains little, if any, chloroacetaldehyde as such, but instead contains its derivative, l,1-'

oxybis-(2-chloroethanol). For convenience, suchsolution will be referred to herein as a chloro acetaldehyde solution, it being understood, however, that the organic solute is present principally as 1,l'-oxybis-(2-chloroethanol) Treatment of concentrated aqueous solutions of chloroacetalde-- hyde with a solid alkali, e. g. sodium hydroxide, results in rapid polymerization of the chloroacetaldehyde and usually, separation of the solution into an aqueous layer and a sticky polymeric.

distilled under vacuum directly from the dilute aqueous mixture, resulting from the reaction be tween vinyl chloride, chlorine and water. By carrying such distillation out under vacuum, e. g.

at from 100 to 300 mm. of Hg absolute pressure,

the step, heretofore considered necessary, of first enriching the reaction mixture with hydrochloric acid may be omitted. As mentioned above, the chloroacetaldehyde in the concentrated solutionobtained as distillate is largely combined with.

water as l,1'-oxybis-(2-chloroethanol).

I have further found that l,l'-oxybis-(2- chloroethanol) can be dehydrated to form chloroacetaldehyde in good yield, by heating the com pound, or a concentrated aqueous solution of the compound, in admixture with an entraining agent, consisting of an inert water-immiscible splitting water from the l,1'-oXybis-(2-chloroorganic liquid having a boiling point below C. at atmospheric pressure, and removing by distillation, water, together with a portion of the entraining agent. Apparently, a reaction of ethanol) molecule to form chloroacetaldehyde occurs quite rapidly at temperatures in the order of from 40 to 70 C. and the chloroacetaldehyde product is stable at these temperatures. ever, the reaction is of an equilibrium type and watermust be removed as it is formed for the reaction to be observable or to permit recovery of the chloroacetaldehyde product.

The process as a whole may be carried out in .a series of steps comprising, (1) distilling at;

subatmospheric pressure the dilute aqueous reac- How- tion mixture, prepared by causing vinyl chloride that may be employed in the'above s'tep"(3-) as entraining agents to remove water by distillation should be solvents for chloroacetaldehyde and preferably have boiling points at atmospheric pressure between 50 C. and 70 C., although solvents having boiling points of from 40C. to 70 C. may be used. They should be inert to the chloroacetaldehyde at the temperatures employed Preferably, the solvents are saturated aliphatic chlorohydrocarbons containing from one to three chlorine atoms in the molec le. Examples of such inertlwater-immiscible organic liquids suitable for use in said step as entraining agents are chloroform, sec-butyl chloride, methylene chloride, non-propyl' chloride and'ethylidene chloride. The entraining agent should, of course, be easily separated from the chloroacetaldehyde. Water-immiscible organic liquids that form constant boiling mixtures with chloroacetaldehyde are not operable in the PIQCES The proportion of entraining agent employed o remove the water byidistillation may vary Within wide limits, A suificient amount of the entr'aining' agent is usually employed so that the temperature-in the distillation vessel does not become greater than the boiling point Zof 1,1- oxylois-(2-chloroethanol). In batch distillation, the process may advantageously be carried out by using from 0.5 to 1.0 parts by. weight of entraining' agent per part of concentrated aqueous chloroacetaldehyde solution or :per part of L-l'rDXybis-(Z-chloroethanol) used, and separating :the entraining a ent from the distillate and returning it to the distillation vessel. In a con- 'tinuous process wherein the entraining agent is separated from the distillate and returned to the distillation column, after operation of the process for a short while; an inventory of 'entraining agent is accumulated'in the system, which is continuously recycled. Inthis instance,

it is merely necessaryithat the entraining agent be present in amount sufiicient to distill together with the water and it may be used iii a'proper' tion' as small as desired, relative'tothe amount of 1,1 -oXybis-'(2-chloroethanol) to "be" eny: drat'ed, i. 'e. the '1,1-Oxybis( 2-chloloethaildl) may-be fed in continuous manner to the distil latibn system containing such inventory of en'- training agent and anhydrous "'chloroacetaldehyde be withdrawn.- I V The mixture is heated under condtions of temperature and pressure such as to distill at temperatures between 40 and 70 C.',' watchtogether with at least a portion of the inert waterimmiscible entraining" agent. "such distillation may be' accomplished by heating "then'i'ixtur at atmospheric pressure; subatm'ospherifpres; sure, or under a" slight sup ratmospheric pressure; depending'ontlie eritrainiii'gagent used.

Fbr iest'ahbi w enseeq meeeaee 1 as the water-entraining agent the reaction may advantageously, be carried out under a pressure of from 10 to 45 inches of Hg, gauge, so as to produce a temperature of from 50 C. to 70 C. in the reaction vessel and the water removed as distillate together with a portion of the methylene chloride.

The distillation is preferably carried out at atmospheric pressure until the dehydration is lsubstantially complete. The remaining entraining agent is usually distilled from the residue under reduced pressure, so as to avoid heating of the chloroacetaldehyde at temperatures above i85 C. .Prolongedheating at 85 0., or at .higher temperatures causes polymerization of a sub- "stantial" portion of" the chloroacetaldehyde, toether with .formation of decomposition products which meniscus to separate from each other and results in lower yields of chloroacetaldehyde. After removal of the entraining agent the anhydrous chloroacetaldehyde may be recovered, prefrably'by continuing the distillation at'suba'tmospheric pressure.

The following examples illustrate practice of the invention, .but are not to be construed as limiting the scope thereof.

Example f A mixture consisting of 1214 grams of solid l,l-oxybi's-(2-chloroethanol) and 900 grams'of chloroform was placed in a round bott'omfla'sk' to the column asrefiux. Distillation was con tinued until the material distilling was clear and apparently free of water. Approximately 11,35

gramsof water was collected in thedi'stillate; The liquid remaining in the reaction ve'ssel'lwa's' fractionally distilled, first at atmospheric pres sure to removemostof the chloroform, and th len under a, reduced pressure ofZQO mm. of Hg abso lute. There was obtained 855 grams or recovered chloroform and 1055.5 areas of 'a'nh" chloroacetaldehyde having the properties':

Boiling point 492512;) at 209 mm. Hg .Secificgravit; 236 a? a e? 2 in heatedtb cjito ,glisti ll eh memes 5 termediate fraction, consisting of a mixture of chloroform and chloroacetaldehyde, distilling at 2570, to 50 C. at 200mm. absolute pressure, and 328 milliliters of chloroacetaldehyde distilling at 50. C. at 200 mm. absolute pressure.

Example 3 A mixture consisting of 600 grams of crystalline 1,1-oxybis-(2-chloroethanol) and 464 grams of methylene chloride were placed in a 1 liter round bottom flask. The mixture was distilled to separate water together with a portion of the methylene chloride, the distillate condensed, and the methylene chloride separated from the aqueous layer and returned to the column as reflux. There was separated 72 milliliters of an aqueous layer having a specific gravity of 1.013 at 25 C. Methylene chloride was recovered from the remaining mixture by fractional distillation at atmospheric pressure and the chloroacetaldehyde distilled at an absolute pressure of 200 mm. of Hg. There was obtained 359.7 grams of chloroacetaldehyde having-a specific gravity of 1.253

at 20 C. and 43.5 grams of solid residue. In addition 37.7 grams of chloroacetaldehyde were collected in a cold trap inserted between the receiver and vacuum pump and 40 grams of solid polymerized chloroacetaldehyde were removed from the condenser.

Example 4 A mixture consisting of 1267 grams of an aqueous solution containing 50 per cent by weight chloroacetaldehyde and 344 grams of sec.-butyl chloride was placed in a round bottom flask equipped with a fractionating column and condenser. The mixture was heated to a temperature between 65 C. and 75 C. to distill therefrom, water together with sec.-butyl chloride. The organic layer of the distillate was separated and returned to the distillation column as reflux. There was separated 661.5 grams of an aqueous layer having a specific gravity of 1.093 at 25 C. After removal of substantially all of the water, the sec.-butyl chloride was separated from the remaining mixture by fractional distillation at atmospheric pressure and the chloroacetaldehyde separated by distillation under a reduced pressure of 300 mm. of mercury absolute pressure. There was obtained 344.1 grams of sec.-butyl chloride, 6.8 grams of an intermediate cut consisting chiefly of a mixture of sec.-butyl chloride and chloroacetaldehyde, 276.6 grams of chloroacetaldehyde having a specific gravity of 1.253 at 20 C. and 191.6 grams of tar-like residue. In addition, 104 grams of solid polymerized chloroacetaldehyde were removed from the condenser and 18.9 grams of liquid product collected in a cold trap, cooled with a mixture of solid carbon dioxide and acetone. This latter product was chiefly chloroacetaldehyde.

Anhydrous chloroacetaldehyde is an extremely corrosive chemical to animal tissue. Vapors of the compound in admixture with air, in concentrations of one per cent by volume, are extreme irritants to mucous membrane. Thus, in preparing and using the compound due precaution should be observed to avoid contact with the material or exposure to the vapors. Processes employing the compound should be carried out with adequate ventilation and suitable protective facilities. For laboratory preparations, employing the chemical compound, the reactions may conveniently be carried out under a hood.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the method or products herein disclosed, provided the steps or products stated in any of the following claims or the equivalent of. such stated steps or products be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a method of making chloroacetaldehyde by causing vinyl chloride and chlorine in gaseous form to react in admixture with water, the steps of distilling the aqueous reaction mixture at from 100 to 300 mm. of Hg, absolute pressure, separating as distillate chloroacetaldehyde in concentration of at least 50 per cent by weight, mixing the distillate with a water-immiscible entraining agent selected from the group consisting of chloroform, sec.-butyl chloride, ethylidene chloride, n-propyl chloride and methylene chloride, heating the mixture at temperatures between 40 and C. to distill therefrom, water together with a portion of the entraining agent at tern peratures between 40 and 70 C., and carrying the distillation to a point until substantially anhydrous chloroacetaldehyde remains in the residue.

2. In a method of making chloroacetaldehyde by causing vinyl chloride and chlorine in. gaseous form to react in admixture with water, the steps of distilling the aqueous reaction mixture at from to 300 mm. of Hg, absolute pressure, separating as distillate chloroacetaldehyde in concentration of at least 50 per cent by weight, mixing the distillate with chloroform, heating the mixture at temperatures between 40 and 85 C., separating therefrom by distillation, water together with a portion of the chloroform and thereafter recovering anhydrous chloroacetaldehyde from. the remaining chloroform.

3. A method of dehydrating 1,l-oxybis- (2- chloroethanol) which comprises, mixing the I of chloroform, sec.-buty1 chloride, ethylidene chloride, n propyl chloride, and methylene chloride, heating the mixture at temperatures between 40 and 85 C. to distill therefrom water together with a portion of the entraining agent at temperatures between 40 and 70 (3., and carrying the distillation to a point until substantially anhydrous chloroacetaldehyde remains in the residue.

4. A method of dehydrating 1,1'-oxybis-(2- chloroethanol) which comprises heating the compound in admixture with chloroform at temperatures between 40 and 85 (3., and separating from the reaction mixture by distillation, water together with a portion of the chloroform.

5. A method of dehydrating 1,1-oxybis-(2- chloroethanol) which comprises heating the compound in admixture with ethylidene chloride at temperatures between 40 and 85 0., and separating from the reaction mixture by distillation, water together with a portion of the ethylidene chloride.

6. In a method of making anhydrous chloroacetaldehyde the steps of mixing an aqueous solution containing at least 50 per cent by weight chloroacetaldehyde with an inert water-immiscible entraining agent having a boiling point between 40 and 70 (3., selected from the group consisting of chloroform, sec.-butyl chloride, ethylidene chloride, n-propyl chloride, and

i 3 r h 5d'rie ehiori'de, heating the mixture at temat uresgbetween 40 and'85" C. to distill theresvatentogether .with a portion of the enng agent .at temperatures --between 40 and "carrying thedistillation to a point until substantially anhydrous -eh-loroacetaldehyde rethe residue and thereafter recovering chloroacetaldehyde from the residue. 7

-17, in .a, method of making anhydrous chloroaeetaldehyde the improvement which comprises I tin 'lilkoxybisd2 chloroethanoi) in admix- With .shioroform at temperatures between separating from the reaction distillation, water split from the 1,1-

y n ggichlproethanol) together with a. por- 9n ,f t e chloroform and thereafter separating enmethod of making anhydrous chloro- Q@t .,hyde :t e "improvement which comprises te filkfijQU-QQUS solution containing at least pent 1, 1.rgggyhisq (2-ch10roethano1) in -ad egetaldehyde from the remaining chloro- :m x iirewi h m thylen eh o id a 'teixiiiexeiute "between-40 and'=85"' (2., separatingtfrom them;- u-lilby' dis i a a e togethe withapeition of e m h ne c ride and thereafte separating chloroacetaldehyde from the remaining methylene chloride.

1C- SIQWE- R ERENCES QITED ilheiollowmg r ierenees areof record mine file of this patent:

URIIED "STATES PAT N'IIS 2 4623194 Feb, @1949 

1. IN A METHOD OF MAKING CHLOROACETALDEHYDE BY CAUSING VINYL CHLORIDE AND CHLORINE IN GASEOUS FORM TO REACT IN ADMIXTURE WITH WATER, THE STEPS OF DISTILLING THE AQUEOUS REACTION MIXTURE AT FROM 100 TO 300 MM. OF HG, ABSOLUTE PRESSURE, SEPARATING AS DISTILLATE CHLOROACETALDEHYDE IN CONCENTRATION OF AT LEAST 50 PER CENT BY WEIGHT, MIXING THE DISTILLATE WITH A WATER-IMMISCIBLE ENTRAINING AGENT SELECTED FROM THE GROUP CONSISTING OF CHLOROFORM, SEC.-BUTYL CHLORIDE, ETHYLIDENE CHLORIDE, N-PROPYL CHLORIDE AND METHYLENE CHLORIDE, HEATING THE MIXTURE AT TEMPERATURE BETWEEN 40* AND 85* C. TO DISTILL THEREFROM, WATER TOGETHER WITH A PORTION OF THE ENTRAINING AGENT AT TEMPERATURES BETWEEN 40* AND 70* C., AND CARRYING THE DISTILLATION TO A POINT UNTIL SUBSTANTIALLY ANHYDROUS CHLORACETALDEHYDE REMAINS IN THE RESIDUE. 